1. Field of the Invention
The invention relates to a liquid-cooled ingot mold for the continuous casting of metals. More particularly, the invention relates to such a mold having mold plates or a chill tube made of copper or a copper alloy, which are connected to a support structure by fastening bolts.
2. Description of Related Art
Mold plates or a chill tube made of copper for continuous casting are usually connected to a support structure by screw connections. The support structure may be a cooling-water tank or an adapter plate. A continuous casting mold for metals is known from DE 195 81 604 T1, in which a uniformly thick mold plate or a chill tube made of copper or a copper material is connected to a support plate made of steel via a plurality of bolts. Particularly in the case of short bolts, the thermally caused expansion of the mold plates or the chill tube in the casting operation results in a non-negligible bending strain and tensile strain in the individual bolts. Depending on the method of fastening the bolts to the mold plate or to the chill tube, there may be a failure of the welded connection in the case of bolts that are welded on, or excessive strain may be exerted on the thread in the case of bolts that are screwed in. In the extreme case, even cracks in the mold plate or in the chill tube may occur. To avoid this, DE 195 81 604 T1 provides for the mold plate and the support plate to be bolted together in a sliding arrangement, so that the mold plate or the chill tube is laterally movable relative to the support plate. This is achieved by using sliding fasteners, and by oversizing the through-holes in the support plate. A lateral or two-dimensional movement of the bolts, and consequently of the mold plate or the chill tube, is possible. In addition to this measure, disk-shaped spring washers are proposed, preferably in a stacked arrangement, in order to maintain the initial tension of the bolt even at high temperatures. In this context, the spring washers are used from the perspective of gear technology as a hinging system having a degree of freedom, that is, as a sliding fit. This solution has the disadvantage that the use of steel spring washers generates a considerable static friction between the spring elements. Due to the plurality of contact surfaces between the spring washers as well as the support plate and the mold plate or the chill tube, the static friction forces add up, so that a stress-free relative displacement of the mold plate/chill tube is impossible. Fundamentally, however, the superposition of the thermally and mechanically induced stresses results in an increased strain on the mold plate or the chill tube, which eventually results in a premature failure and a reduction in the service life of the ingot mold.